The invention relates to a leaf seal for sealing off a shaft rotating around an axis, particularly in a gas turbine. The invention further relates to a gas turbine having such type of leaf seal as well as a process for producing such type of leaf seal.
Various seals can be used for sealing off gaps. For example, brush seals are often used in engine construction in order to seal off gaps between a rotor and a stator. Due to their mechanical integrity, brush seals are contact seals that themselves are subject to wear as are their friction partner during operation. In addition, brush seals can only be used up to a differential pressure of about 12 bar.
Leaf seals, which can be used in environments with very high pressure differences and which furthermore take longer to exhibit wear than brush seals due to their axial stiffness, offer a solution to this problem. One such type of leaf seal is known, for example, from German Patent Document DE 10 2004 020 378 A1 and comprises a plurality of leaves, which are connected to one another through electron beam welding. Alternatively, it is known to thread the individual leaves of a leaf seal separately into a corresponding receptacle of the housing.
Both structural types are, however, very complex and extremely expensive, because leaf seals in the engine sector, for example, may comprise up to 4000 leaves or more. Due to the comparably delicate design of the individual leaves, the known leaf seals also cannot be prefabricated in a practical overall size for engine applications and cannot be adapted to different installation situations, or can only be done so at great expense. In addition, a correspondingly great deal of effort is required in order to ensure sufficient reproducibility of such individually produced leaf seals.
The object of the present invention is to obtain a leaf seal of the aforementioned type, which is simple to produce and simple to adapt to various installation situations. A further object of the invention is the provision of a process for producing the leaf seal.
A first aspect of the invention relates to a leaf seal for sealing off a shaft rotating around an axis, particularly in a gas turbine, comprising a plurality of leaves arranged spaced apart from one another, in which a provision according to the invention is that the leaves are produced integrally with a basic element supporting the leaves by a generative production process. In other words, different from the prior art, a provision is that the leaf seal is generatively produced, in which the individual leaves are connected to one another by a basic element. This makes the leaf seal according to the invention quicker and easier to produce. Furthermore, the generative production enables much design freedom and flexibility, which means that the leaf seal according to the invention can also be easily adapted to different installation situations. The integral design enables, for example, simple modification of the intervals between individual leaves or sealing elements, so that the leaf seal can be quickly and simply adapted to any preferred shaft diameter or to any gap geometry. In addition, the stiffness of any individual leaf can be infinitely adapted to the requirements at hand. In particular, the generative production enables a very large spectrum of leaf thicknesses, which means that the individual leaves can have thicknesses between 0.1 mm and 4 mm, for example, regardless of the average thicknesses among one another. It is also possible for the radial design height of each individual leaf as well as the individual distances between adjacent leaves to be optimally adapted to the individual installation situation. Regardless of this, the shape or the geometry of the individual leaves can be optimally adapted to the individual requirements. In addition to adjusting the individual geometry, it is also possible to vary the material used within the scope of the generative production process once or multiple times in order to selectively adjust certain properties of the leaf seal. Finally, the basic element can also be formed independently of the leaves. For example, the basic element can be formed as a shroud, which is produced as an integral unit together with the leaves and can be installed in any housing configurations as a leaf seal. In particular, very large or very small sizes can also be produced with generative production. Due to the integral design, the tolerances are also significantly lower than with the previously known leaf seals. In addition, the assembly time of the leaf seal is reduced significantly, because no leaf seals have to be threaded in or welded due to the integral design. Instead, the entire leaf seal can be integrally produced and, in the simplest case, directly installed without further processing steps. This enables costs to be reduced by a factor of 10 or more. The generative production method additionally increases the reproducibility of the leaf seal.
In an advantageous embodiment of the invention, a provision is that at least one leaf has a nonuniform cross-sectional geometry. In other words, a provision is that one, more, or all leaves have a nonuniform cross-sectional geometry. For example, one or more local thickening and/or thinning areas may be provided on each leaf. In this manner, the elastic bending behavior of each leaf can be optimally adjusted, for example.
Additional advantages result in that at least one leaf has a reduced cross-sectional thickness in the area of the basic element. Such type of recess facilitates relative tipping of the particular leaf with respect to the basic element, so that improved contact can be achieved at an assigned shaft and thus an improved sealing effect. Basically, multiple or all leaves of such type can be formed.
Alternatively or in addition to this, a provision may be that at least one leaf includes a spacer element for adjusting a minimum distance to an adjacent leaf. This enables the adjustment of a minimum gap between two adjacent leaves and thus a defined minimum porousness of the leaf seal for operating fluid. The spacer element can be formed, in the simplest embodiment, as a thickened area of the leaf, for example, and preferably formed on the basic element opposite the end area of the leaf.
Other possibilities for individual adjustment of the sealing effect and the geometry of the leaf seal are enabled in that at least one leaf is arranged at a predetermined placement angle and/or at a predetermined adjustment angle with regard to a longitudinal axis of the basic element. In other words, the tilt angle of the leaf and/or the angle between the longitudinal axis of the basic element and the vein of the particular leaf can be essentially freely selected. The tilt angle and/or the angle between the longitudinal axis of the basic element and the vein of the particular leaf can thus take on values, independently from one another, for example of 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, or 90°, as well as corresponding intermediate values.
In another advantageous embodiment of the invention, a provision is that the basic element includes at least one fastener for fastening the leaf seal to a component, particularly to a housing part. This enables a particularly simple adaptability of the leaf seal to various housing types, because the geometry and arrangement of the fastener may also essentially be freely selected.
In another advantageous embodiment of the invention, a provision is that the at least one fastener is arranged on a side of the basic element facing away from the leaves. This enables particularly easy fastening of the leaf seal and assigned mount.
In another advantageous embodiment of the invention, a provision is that the at least one fastener be produced integrally with the basic element by the generative production process. Although it is essentially of course also conceivable for the at least one fastener to be subsequently placed on the basic element, the integral production of the at least one fastener to the basic element represents a particularly simple and quick design option for equipping the basic element with the at least one fastener.
Additional advantages result in that at least one leaf has a winglet at its upstream and/or downstream end area. In other words, a provision according to the invention is that at least one, more, or all leaves have an upstream and/or downstream end area, regarding a subsequent installation situation, which is arranged at an adjustment angle with respect to the adjacent leaf area. Such winglets advantageously increase the sealing effect of the leaf seal, because they partially block straight-line passageway for the gas flow in the axial direction, but do not seal it off completely. The gas flow is instead rerouted through the winglet or through the winglets, so that a type of labyrinth seal results.
Additional advantages result in that the basic element and/or at least one seal includes at least one recess. In addition to weight optimization of the leaf seal, this also enables the assurance of even pressure distribution as well as the adaptation of basic stiffness of the leaf (or leaves) or of the basic element.
In another advantageous embodiment of the invention, a provision is that the basic element be formed so as to be elastically deformable and/or shaped as an annular segment in the longitudinal section. This enables a particularly simple and quick assembly of the leaf seal in a cylindrical gap, particularly in a gas turbine.
A further aspect of the invention relates to a gas turbine, particularly an aircraft engine, having a housing, in which at least one leaf seal is arranged around a rotor according to one of the preceding exemplary embodiments, in order to reduce a flow of fluid from a high-pressure side to a low-pressure side of the rotor. The resulting features and the advantages thereof are contained in the previous descriptions of the first aspect of the invention, in which advantageous embodiments of the leaf seal can be considered advantageous embodiments of the gas turbine and vice versa.
The sealing effect can be significantly increased in a simple and economical manner in that at least two leaf seals are provided according to the first aspect of the invention and preferably offset in the axial direction with respect to a rotational axis of the rotor, arranged one after the other. The sealing effect can be particularly precisely adjusted in addition due to the level of the relative offsetting with respect to one another. In doing so, it can essentially be provided that the at least two leaf seals be initially produced as a single piece by the generative production process. If necessary, the single-piece leaf seal can subsequently be divided into two or more individual leaf seals.
A third aspect of the invention relates to a process for producing a leaf seal for sealing off a shaft rotating around an axis, particularly in a gas turbine, in which the leaf seal includes a plurality of leaves arranged spaced apart from one another. In doing so, a provision according to the invention is that the leaves be produced integrally together with a basic element supporting the leaves by a generative production process. The resulting features and the advantages thereof are contained in the preceding descriptions of the first and the second aspect of the invention, in which advantageous embodiments of the leaf seal and/or of the gas turbine can be considered advantageous embodiments of the process according to the invention and vice versa. The process according to the invention in this case is essentially not limited to a certain generative production process. For example, known generative processes such as selective laser melting (SLM), direct metal laser sintering (DMLS), and/or electron beam processes can be used.
In an advantageous embodiment of the invention, a provision is that a support structure be formed on the leaf seal during the generative production process and be preferably subsequently removed. With the assistance of a support structure, particularly damage to the leaves is advantageously avoided during the generative production process. The support structure can be formed on an end area of the leaves opposite the basic element and preferably then removed after production of the leaf seal.
Additional features of the invention result from the claims, the exemplary embodiments, and the drawings. The features and feature combinations listed previously in the description as well as the features and feature combinations listed in the exemplary embodiment in the following can be used not only in the respectively indicated combination, but also in other combinations, without going beyond the scope of the invention.